WPF BitmapFrame Sınıfı

Create metodu - stream + creation options +  cache options
Şöyle yaparız.

public static async Task<BitmapSource> GetNewImageAsync(Uri uri)
{
  var httpClient = new HttpClient();

  using (var response = await httpClient.GetAsync(uri))
  {
    if (response.IsSuccessStatusCode)
    {
      using (var stream = new MemoryStream())
      {
        await response.Content.CopyToAsync(stream);
        stream.Seek(0, SeekOrigin.Begin);

        return BitmapFrame.Create(
          stream, BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
      }
    }
  }

  return null;
}